RV sizing for regulator failure case
RV sizing for regulator failure case
(OP)
I am sizing an RV for a regulator failure scenario. All the literature I can find basically states that to determine the required capacity of the RV, one must calculate the flow rate through the wide open regulator and size the RV to relieve that flow rate. It seems as if the physical interpretation of this would be that the entire flow through the failed regulator would now flow through the RV.
1) Can any credit be given due to the fact that the original flow path is still open and will flow at least the original flow rate (pre-regulator failure) through it? i.e. Can an RV with a lower capacity than the wide open regulator be used as long as the sum of the flow out equals the flow through the failed regulator?
2) If I sized the RV in this manner, would there be any pressure accumulation in the line beyond the RV setpoint?
The fluid is service water at ambient temperature and 80psig, with the regulator set to 10psig and a flow rate of 28 USgpm (flow rate prior to regulator failure).
Any advice is much appreciated
1) Can any credit be given due to the fact that the original flow path is still open and will flow at least the original flow rate (pre-regulator failure) through it? i.e. Can an RV with a lower capacity than the wide open regulator be used as long as the sum of the flow out equals the flow through the failed regulator?
2) If I sized the RV in this manner, would there be any pressure accumulation in the line beyond the RV setpoint?
The fluid is service water at ambient temperature and 80psig, with the regulator set to 10psig and a flow rate of 28 USgpm (flow rate prior to regulator failure).
Any advice is much appreciated





RE: RV sizing for regulator failure case
What you're sizing is an RV for an isolable/restricted flow pressure boundary (piping, PV, HX, etc.). The scenario input is that the flow into said boundary is full open flow downstream of a failed regulator. You would need to size the RV for full flow whether there was a regulator or not. What you are taking credit for is that the regulator creates a pressure drop (even at full open).
What you might be able to take credit for is flow out of the pressure boundary that cannot be isolated.
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RE: RV sizing for regulator failure case
That confirms what I would have instinctively thought, I just haven't seen a situation such as this discussed in any codes or reference documents.
RE: RV sizing for regulator failure case
Best regards
Morten
RE: RV sizing for regulator failure case
You can take credit for continuous system usage other than the SRV if that usage absolutely WILL be there at all times regardless of ANY consideration. If it's possible for something silly like for a forklift to fall out of a 747 and squash the downstream piping---you have a weak case.
RE: RV sizing for regulator failure case